Ask HN: Can anyone recommend a good security auditor / pen tester?

I'm acting on behalf of a company that believes that they have been infiltrated / hacked. I can't go into much details here.

I need some recommendations on people / companies that can help:

- security audit (company servers / desktops / laptops)

- penetration testing (both network and social engineering)

Company is based in the UK. Discretion is very important to the client. You are likely to be asked for references / work experience. They might also need you to sign an NDA.

My email in profile.

P.S. I'm not sure if this would be better in the "seeking freelancers" section of HN. Please let me know if that is the case, and I'll delete this and move it there.